Method for retracting a partially extended sliding camshaft actuator pin

ABSTRACT

A method for retracting a partially extended pin of a sliding camshaft actuator having first and second pins being selectively actuatable by adjacent first and second magnetic field generating coils includes determining if the first or the second pin is partially extended after engine ignition. A partially extended first pin is retracted with flux linkage created by the second magnetic field generating coil being coupled unto the first magnetic field generating coil, and a partially extended second pin is retracted with flux linkage created by the first magnetic field generating coil being coupled unto the second magnetic field generating coil.

TECHNICAL FIELD

The present invention generally relates to sliding camshaft actuatorsfor variable valve lift (VVL) systems, and more particularly relates toa method for retracting a partially extended sliding camshaft actuatorpin.

BACKGROUND

Internal combustion engines include intake and exhaust valves that canbe actuated by cam lobes of at least one camshaft. In someconfigurations the camshafts are constructed with sliding camshaftassemblies having multiple steps for varying the lift distance of anengine valve. For example, a two-step sliding camshaft may include ahigh lift cam lobe position for lifting an engine valve to a maximumdistance, and a low lift cam lobe position for lifting the engine valvebelow the maximum lift distance.

At least one sliding camshaft actuator is fixed on an internalcombustion engine for changing position between the multiple cam lobes.Particularly, at least one actuator pin of a camshaft actuator isoperative to selectively engage displacement grooves configured on theperiphery of camshaft barrels formed on the sliding camshaft assembly.As the camshaft assembly rotates, an actuator pin is selected to moveinto a displacement groove of the camshaft barrel which causes thesliding camshaft assembly to shift into a different position along thecamshaft axis. When a sliding camshaft shifts position, the intakeand/or exhaust valves are actuated differently in accordance with thechanged cam lobe position, e.g., a sliding camshaft may move from a highlift cam lobe position to a low lift cam lobe position, which in turnwill cause the engine operation to be different.

Thus, the sliding camshaft actuator is an important component in theproper operation of a VVL sliding camshaft system, particularly theactuator's pin extension into, and retraction from, the displacementgrooves into the camshaft barrels. If an extended actuator pin is onlypartially retracted for any reason then a subsequent shift command couldresult in the partially retracted pin being broken off or some otherdamage caused to the sliding camshaft system. Thus, there is a need fora reliable means of ensuring that a partially extended actuator pin canbe caused to fully retract to prevent damage to the sliding camshaftsystem.

BRIEF SUMMARY

One or more exemplary embodiments address the above issue by providing amethod for retracting a partially extended sliding camshaft actuatorpin.

According to an aspect of an exemplary embodiment, a method forretracting a partially extended pin of a sliding camshaft actuatorhaving first and second pins being selectively actuatable by adjacentfirst and second magnetic field generating coils includes determining ifthe first or the second pin of the sliding camshaft actuator ispartially extended after engine ignition. Still another aspect accordingto the exemplary embodiment includes energizing the first magnetic fieldgenerating coil of the sliding camshaft actuator when the second pin ispartially extended. And another aspect includes retracting the partiallyextended second pin with flux linkage created by the first magneticfield generating coil being coupled unto the second magnetic fieldgenerating coil and the second pin. And yet another aspect of theexemplary embodiment includes energizing the second magnetic fieldgenerating coil of the sliding camshaft actuator when the first pin ispartially extended. And still another aspect includes retracting thepartially extended first pin with flux linkage created by the secondmagnetic field generating coil being coupled unto the first magneticfield generating coil and the first pin.

Still another aspect of the exemplary embodiment includes detecting aposition of a three step intake sliding camshaft. And another aspectwherein the three step intake sliding camshaft comprises at least oneposition indicator barrel. And a further aspect wherein the three stepintake sliding camshaft further comprises high lift lobe, low lift lobe,and deactivate lobe positions. Yet a further aspect wherein detectingfurther comprises using a Hall Effect sensor for detecting position ofthe three step intake sliding camshaft. And still another aspect inaccordance with the embodiment wherein detecting further comprisessensing position identifying tracks configured on the at least oneposition indicator barrel.

Another aspect in accordance with the exemplary embodiment whereinretracting occurs when a partially extended pin is aligned over a lowlift lobe position.

And another aspect wherein energizing occurs when the at least oneposition indicator barrel is positioned to prevent a retracted pin frompartially extending.

BRIEF DESCRIPTION OF THE DRAWINGS

The present exemplary embodiment will hereinafter be described inconjunction with the following drawing figures, wherein like numeralsdenote like elements, and

FIG. 1 is an illustration of an intake and an exhaust sliding camshaftconfiguration for a 4 cylinder internal combustion engine in accordancewith aspects of an exemplary embodiment;

FIG. 2 is an illustration of an intake sliding camshaft configurationwith position shifting camshaft actuators in accordance with aspects ofthe exemplary embodiment;

FIG. 3 is an illustration of a cross sectional view of a slidingcamshaft actuator in accordance with aspects of the exemplaryembodiment;

FIG. 4a is an illustration of a portion of an intake sliding camshaftincluding a camshaft actuator with a partially extended pin aligned overa low lift cam lobe in accordance with aspects of the exemplaryembodiment;

FIG. 4b is an illustration of a portion of an intake sliding camshaft intransition from a high lift cam lobe position to low lift cam lobeposition including a camshaft actuator with a partially extended pin inaccordance with aspects of the exemplary embodiment;

FIG. 4c is an illustration of a portion of an intake sliding camshaftafter the partially extended actuator pin fractured during thetransition from the high lift lobe position to the low lift valveposition in accordance with aspects of the exemplary embodiment;

FIG. 5 is an illustration of a functional view of a sliding camshaftactuator with a partially extended pin being retracted by an additionalmagnetic force generated by the energized adjacent coil in accordancewith aspects of the exemplary embodiment;

FIG. 6 is an illustration of an algorithm for retracting a partiallyextended sliding camshaft actuator pin in accordance with the exemplaryembodiment.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and isnot intended to limit the embodiment or the application and usesthereof. Furthermore, there is no intention to be bound by any theorypresented in the preceding background or the following detaileddescription.

In accordance with the disclosed embodiment, FIG. 1 is an illustrationof an intake and an exhaust sliding camshaft configuration for a 4cylinder internal combustion engine camshaft system 10 in accordancewith aspects of an exemplary embodiment. It is appreciated that the 4cylinder embodiment is merely exemplary and the concept of slidingcamshaft barrel position sensing may be applied to other multiplecylinder engine camshaft system configurations, e.g., 5, 6, 8, 9, or 12,without exceeding the scope of the invention.

The camshaft system 10 includes at least one sliding camshaft having atleast one camshaft barrel. In the case, the camshaft system 10 includesa three (3) step intake sliding camshaft 12 and a two (2) step exhaustsliding camshaft 14. For shifting the position of the three step intake12 and two step exhaust 14 sliding camshafts, at least one camshaftactuator 16 is provided in selective communication to the camshafts andcommanded on and off by a control module, e.g., engine control module(not shown). Particular to this embodiment, camshaft system 10 includesa plurality of actuators (16 a-16 f) with actuators (16 a-16 d) beingoperative for shifting the three step intake sliding camshaft 12, andactuators (16 e-16 f) being operative for shifting the two step exhaustsliding camshaft 14 when commanded by the controller.

Referring now to FIG. 2, the three step intake sliding camshaft 12includes two sliding lobe assemblies, 18 and 20. Each sliding lobeassembly (18, 20) includes at least one position indicator camshaftbarrel. Position indicator camshaft barrels 22 and 24 are fixed on thesliding lobe assembly 18, and the position indicator camshaft barrels 26and 28 are fixed to sliding lobe assembly 20 in accordance with theexemplary embodiment. Referring to the enlarged view of the sliding lobeassembly 18 of the three step sliding intake camshaft 12, included is ahigh lift cam lobe position 29, a low lift cam lobe position 30, and adeactivated cam lobe position 31 for providing the three steps of thecamshaft in accordance with the exemplary embodiment. The high lift camlobe position 29 refers to the air intake valves (34-40) being opened tothe maximum position each time the three step intake sliding camshaft 12rotates 360° while in this lobe position. The low lift cam lobe position30 refers to the air intake valves being opened to a less than maximumlobe position each time the intake sliding camshaft 12 rotates 360° andthe deactivated cam lobe position 31 refers to the air intake valves notbe opened at all each time the three step intake sliding camshaft 12rotates 360°. The three step intake sliding camshaft 12 also includespipe journals 32 for at least maintaining spacing between sliding lobes.

Referring now to FIG. 3, an illustration 50 of a cross sectional view ofa sliding camshaft actuator (16 a) is provided in accordance withaspects of the exemplary embodiment. The sliding camshaft actuator 16 aincludes a first magnetic field generating coil 52 wound on a spool 53that shrouds a sliding armature 54 within its core. A magnet 56 isdisposed between metal plates 68 and fixed at a bottom end of thesliding armature 54. The first magnetic field generating coil 52, thesliding armature 54, and magnet 56 are operative to cause a firstactuator pin 58 to be extended into a camshaft barrel as necessary forpurposes of shifting the position of the three step intake slidingcamshaft 12 in accordance with aspects of the exemplary embodiment.

The sliding camshaft actuator 16 a also includes a second magnetic fieldgenerating coil 60 wound on a spool 61 that shrouds another slidingarmature 62. A second magnet 64 is also disposed between metal plates 68and fixed at a bottom end of the sliding armature 62. The secondmagnetic field generating coil 60, the sliding armature 62, and magnet64 are operative to cause a second actuator pin 66 to be extended into acamshaft barrel as necessary for purposes of shifting the position ofthree step sliding intake camshaft 12 in accordance with the exemplaryembodiment.

Referring now to FIG. 4a , an illustration 70 of a portion of a threestep intake sliding camshaft 12 including a camshaft actuator 16 a witha partially extended pin 58 aligned over a low lift cam lobe 30 isprovided in accordance with aspects of the exemplary embodiment. Aposition detection sensor 72 is operative to detect the position of thethree step intake sliding camshaft 12 by sensing position identifyingtracks (not shown) configured on the at least one position indicatorbarrel 22. For example, after engine ignition the position detectionsensor 72 will detect a position identifying track on the at least oneposition indicator barrel 22 that indicates the three step intakesliding camshaft 12 is in a high lift cam lobe position 29 for actuatingintake valves 80. When the intake sliding camshaft 12 is commanded toshift position, another position identifying track may indicate that thethree step intake sliding camshaft 12 is in a low lift cam lobe position30.

In accordance with the exemplary embodiment, the position detectionsensor 72 operates to indicate when the three step intake slidingcamshaft 12 is in a position where a potential exists for a partiallyextended actuator pin 58 can be aligned over a low lift cam lobe 30. Insuch case, it is probable that the partially extended actuator pin willbe bent or fractured when the three step intake sliding camshaft 12 iscommanded to shift toward direction 78 such that an intake valves 80 aretransitioned from a high lift cam lobe position 29 to a low lift camlobe position 30.

In FIG. 4b , an illustration of a portion of an intake sliding camshaft12 in transition from a high lift cam lobe position 29 to low lift camlobe position 30 in accordance with aspects of the exemplary embodimentis provided. As the intake sliding camshaft 12 rotates in the direction76, the sliding camshaft actuator 16 a has a partially extended pin 58aligned over a low lift cam lobe 29. The sliding camshaft actuator 16 ais commanded to extend pin 66 into a displacement groove 74 to cause thethree step intake sliding camshaft to shift the valves 80 from a highlift cam lobe position 29 to a low cam lobe position 30. As the slidinglobe assembly 18 begins to move in direction 78, the partially extendedactuator pin 58 is subjected to a force from the position indicatorbarrel 22. As shown in FIG. 4c , the increasing force on the partiallyextended pin 58 from the position indicator barrel 22 causes it to bendand ultimately fracture such that the actuator would have to bereplaced. Also, the actuator pin 66 is subjected to a bending forcewhile disposed in the displacement groove 74 causing further damage tothe camshaft actuator 16 a.

Referring to FIG. 5, an illustration 90 of a functional view of asliding camshaft actuator 16 a with a partially extended pin beingretracted in accordance with aspects of the exemplary embodiment isprovided. From left to right, the camshaft actuator 16 a is shown havinga partially extended first pin 58 while a second pin 66 is in a fullyretracted position over the position indicator barrel 22. After theengine is ignited, the position detection sensor 72 (not shown) detectsthe position of position indicator barrel 22 to determine when the threestep intake sliding camshaft 12 is in a position where there is apotential for a partially extended pin condition to exist. Neither ofthe first magnetic field generating coil 52 nor second magnetic fieldgenerating coil 60 are energized in this instance. But, there is amagnetic attraction force 91 between the magnet 56 and the metal plate68 of the first magnetic field generating coil 52. However, the magneticattraction force 91 is not strong enough to retract the partiallyextended pin 58.

Therefore, when it is determined that a potential for a partiallyextended pin condition exists, in order to cause the partially extendedfirst pin 58 to retract, the second magnetic field generating coil 60 isenergized to create magnetic field flux linkage 92 with the firstmagnetic field generating coil 52 and the partially extended pin 58 suchthat an additional magnetic attraction force 94 is imposed on thepartially extended actuator pin 58 causing it to move to the fullyretracted position. When the second magnetic field generating coil 60 isenergized, it creates a repelling force 95 which is directed onto themagnet 64 influencing the actuator pin 66 to attempt to extend outward.However, the second actuator pin 66 is aligned over the positionindicator barrel 22 such that it will not extend or will be extendedinto the displacement groove 74 and be moved back into a full retractedposition when it exits the displacement groove 74 and the secondmagnetic field generation coil 60 is de-energized.

Referring now to FIG. 6, an illustration of an algorithm 100 forretracting a partially extended sliding camshaft actuator pin inaccordance with the exemplary embodiment is provided. At block 110, themethod begins with determining if a first or second pin of a camshaftactuator is partially extended after engine ignition using the threestep intake sliding camshaft position detection sensor. At block 120, ifit is determined by the position detection sensor that a potentialexists for the first actuator pin to be extended then the methodproceeds to block 130 for energizing the second magnetic fieldgenerating coil, and then to block 140 for retracting the first actuatorpin with flux linkage being created by the energized second magneticfield generating coil being coupled onto the first magnetic fieldgenerating coil and the partially extended first pin.

At block 150, if it is determined by the position detection sensor thata potential exists for the second actuator pin to be extended then themethod proceeds to block 160 for energizing the first magnetic fieldgenerating coil, and then to block 170 for retracting the secondactuator pin with flux linkage being created by the energized firstmagnetic field generating coil being coupled onto the second magneticfield generating coil and the partially extended second pin.

At block 180, the method continues with determining if the engineignition is still on. If the engine ignition is still on then the methodcontinues returns to block 110 to repeat the process. If the ignition isturned off then the process ends until the next engine ignition.

The detailed description provides those skilled in the art with aconvenient road map for implementing the exemplary embodiment orexemplary embodiments. Many modifications and variations will beapparent to those of ordinary skill in the art without departing fromthe scope and spirit of the invention. While at least one exemplaryembodiment has been presented in the foregoing detailed description ofthe invention, it should be appreciated that a vast number of variationsexist. It should also be appreciated that the exemplary embodiment orexemplary embodiments are only examples, and are not intended to limitthe scope, applicability, or configuration of the invention in any way.Rather, the foregoing detailed description will provide those skilled inthe art with a convenient road map for implementing an exemplaryembodiment of the invention. It being understood that various changesmay be made in the function and arrangement of elements described in anexemplary embodiment without departing from the scope of the inventionas set forth in the appended claims.

What is claimed is:
 1. A method for retracting a partially extended pinof a sliding camshaft actuator having first and second pins beingselectively actuatable by adjacent first and second magnetic fieldgenerating coils comprising: determining if the first or the second pinis partially extended after engine ignition; energizing the firstmagnetic field generating coil of the sliding camshaft actuator when thesecond pin is partially extended; retracting the partially extendedsecond pin with flux linkage created by the first magnetic fieldgenerating coil being coupled unto the second magnetic field generatingcoil and the second pin; energizing the second magnetic field generatingcoil of the sliding camshaft actuator when the first pin is partiallyextended; and retracting the partially extended first pin with fluxlinkage created by the second magnetic field generating coil beingcoupled unto the first magnetic field generating coil and the first pin.2. The method of claim 1 further comprises detecting a position of athree step intake sliding camshaft.
 3. The method of claim 2 wherein thethree step intake sliding camshaft comprises at least one positionindicator barrel.
 4. The method of claim 3 wherein the three step intakesliding camshaft further comprises high lift lobe, low lift lobe, anddeactivate lobe positions.
 5. The method of claim 4 wherein detectingfurther comprises using a Hall Effect sensor for detecting position ofthe three step intake sliding camshaft.
 6. The method of claim 5 whereindetecting further comprises sensing position identifying tracksconfigured on the at least one position indicator barrel.
 7. The methodof claim 6 wherein retracting occurs when a partially extended pin isaligned over a low lift lobe position.
 8. The method of claim 7 whereinenergizing occurs when the at least one position indicator barrel ispositioned to prevent a retracted pin from partially extending.
 9. Amethod for retracting a partially extended pin of a sliding camshaftactuator having first and second pins being selectively actuatable byadjacent first and second magnetic field generating coils comprising:detecting a position of a three step intake sliding camshaft afterengine ignition wherein the three step intake sliding camshaft includeshigh lift lobe, low lift lobe, and deactivate lobe positions; retractinga partially extended second pin with flux linkage created by the firstmagnetic field generating coil being coupled unto the second magneticfield generating coil and the second pin when the second pin is alignedover a low lift lobe position; and retracting a partially extended firstpin with flux linkage created by the second magnetic field generatingcoil being coupled unto the first magnetic field generating coil and thefirst pin when the first pin is aligned over a low lift lobe position.10. The method of claim 9 further comprises energizing the firstmagnetic field generating coil of the sliding camshaft actuator when thesecond pin is partially extended.
 11. The method of claim 10 furthercomprises energizing the second magnetic field generating coil of thesliding camshaft actuator when the first pin is partially extended. 12.The method of claim 11 wherein the three step intake sliding camshaftcomprises at least one position indicator barrel.
 13. The method ofclaim 12 wherein detecting further comprises using a Hall Effect sensorfor detecting position of the three step intake sliding camshaft. 14.The method of claim 13 wherein using a Hall Effect sensor furthercomprises sensing position identifying tracks configured on the at leastone position indicator barrel.
 15. The method of claim 12 energizingoccurs when the at least one position indicator barrel is positioned toprevent a retracted pin from partially extending.